Machado C. Comment on Canadian clinical practice guideline on brain death. November 2023 Canadian Anaesthetists? Society JournalFollow journal DOI: 10.1007/s12630-023-02660-7

Abstract

To the Editor,
Shemie et al. constructed the ‘‘2023 Clinical Practice
Guideline on a brain-based definition of death and criteria for
its determination after arrest of circulation or neurologic
function in Canada,’’ providing a biomedical definition of
death.1 This Guideline remarked, ‘‘Death is defined as the
permanent cessation of brain function (i.e., brain function is
lost, will not resume spontaneously, and will not be restored
through intervention) and is characterized by the complete
absence of any form of consciousness (wakefulness and
awareness) and the absence of brainstem reflexes, including
the ability to breathe independently.’’1
The World Brain Death Project (WBDP) similarily
defined brain death/death by neurologic criteria (BD/DNC)
as ‘‘the complete and permanent loss of brain function as
defined by an unresponsive coma with loss of capacity for
consciousness, brainstem reflexes, and the ability to
breathe independently.’’2
I proposed that death is the ‘‘irreversible loss of both
components of consciousness–arousal and awareness–
which provides the key human attributes and the highest
level of control in the hierarchy of integrating functions
within the human organism.’’ The critical attribute of life is
consciousness. Korein and Machado discussed that the brain
provides the highest level of control within the organism.3
Pallis used ‘‘capacity of consciousness,’’ referring to
‘‘arousal,’’ one component of consciousness.4 Therefore, I
propose to rephrase the WBDP definition ‘‘the complete
and permanent loss of brain function as defined by an
unresponsive coma’’ with ‘‘loss of both components of
consciousness—arousal and awareness—and the ability
to breathe.’’3
The Guideline also proposed that ‘‘residual brain cell
activity that is not associated with the presence of
consciousness or brainstem function does not preclude
death determination (e.g., posterior pituitary antidiuretic
hormone release, temperature control, or cellular-level
neuronal activity).’’1
The hypothalamus plays a key role in the central
control of the autonomic nervous system (ANS). The
hypothalamus contains neurons that send axons to the
preganglionic neurons for both the sympathetic and
parasympathetic nervous systems, regulating the
autonomic outflow. If there is a residual hypothalamic
function in patients with brain death, finding a remaining
autonomic function is possible. I reported on a patient
who showed remaining heart rate variability (HRV) in
very low-frequency waves after completing a BD/DNC
clinical diagnosis. All HRV bands were preserved in Jahi
McMath and showed autonomic reactivity to ‘‘Mother
Talks’’ stimulation, suggesting enduring awareness.
Hence, I described a new state of disorder of
consciousness.5

Full text

CORRESPONDENCE
Comment on: Canadian clinical practice guideline on brain death
Calixto Machado, MD, PhD, FAAN
Received: 27 September 2023 / Revised: 27 September 2023 / Accepted: 27 September 2023
ÓCanadian Anesthesiologists’ Society 2023
Keywords brain death clinical practice guideline 
consciousness hypothalamus Jahi McMath
To the Editor,
Shemie et al. constructed the ‘‘2023 Clinical Practice
Guideline on a brain-based definition of death and criteria for
its determination after arrest of circulation or neurologic
function in Canada,’’ providing a biomedical definition of
death.
1
This Guideline remarked, ‘‘Death is defined as the
permanent cessation of brain function (i.e., brain function is
lost, will not resume spontaneously, and will not be restored
through intervention) and is characterized by the complete
absence of any form of consciousness (wakefulness and
awareness) and the absence of brainstem reflexes, including
the ability to breathe independently.’’
1
The World Brain Death Project (WBDP) similarily
defined brain death/death by neurologic criteria (BD/DNC)
as ‘‘the complete and permanent loss of brain function as
defined by an unresponsive coma with loss of capacity for
consciousness, brainstem reflexes, and the ability to
breathe independently.’’
2
I proposed that death is the ‘‘irreversible loss of both
components of consciousness–arousal and awareness–
which provides the key human attributes and the highest
level of control in the hierarchy of integrating functions
within the human organism.’’ The critical attribute of life is
consciousness. Korein and Machado discussed that the brain
provides the highest level of control within the organism.
3
Pallis used ‘‘capacity of consciousness,’’ referring to
‘‘ arousal,’’ one component of consciousness.
4
Therefore, I
propose to rephrase the WBDP definition ‘‘the complete
and permanent loss of brain function as defined by an
unresponsive coma’’ with ‘‘loss of both components of
consciousness—arousal and awareness—and the ability
to breathe.’’
3
The Guideline also proposed that ‘‘residual brain cell
activity that is not associated with the presence of
consciousness or brainstem function does not preclude
death determination (e.g., posterior pituitary antidiuretic
hormone release, temperature control, or cellular-level
neuronal activity).’’
1
The hypothalamus plays a key role in the central
control of the autonomic nervous system (ANS). The
hypothalamus contains neurons that send axons to the
preganglionic neurons for both the sympathetic and
parasympathetic nervous systems, regulating the
autonomic outflow. If there is a residual hypothalamic
function in patients with brain death, finding a remaining
autonomic function is possible. I reported on a patient
who showed remaining heart rate variability (HRV) in
very low-frequency waves after completing a BD/DNC
clinical diagnosis. All HRV bands were preserved in Jahi
McMath and showed autonomic reactivity to ‘‘Mother
Talks’’ stimulation, suggesting enduring awareness.
Hence, I described a new state of disorder of
consciousness.
5
This article is accompanied by a reply. Please see Can J Anesth 2023;
https://doi.org/10.1007/s12630-023-02661-6.
C. Machado, MD, PhD, FAAN (&)
Institute of Neurology and Neurosurgery, 10400, 29 y D,
Vedado, Havana, Cuba
Institute of Neurology and Neurosurgery, Havana, Cuba
e-mail: cmachado180652@gmail.com
123
Can J Anesth/J Can Anesth
https://doi.org/10.1007/s12630-023-02660-7

Studying hypothalamic-pituitary functions by laboratory
screening in BD/DNC determination would be time
consuming. Nonetheless, if a suspected brain-dead patient
has an irreversible loss of both components of
consciousness, the diagnosis of BD/DNC can be
completed despite residual hypothalamic function. The
ANS should be assessed if doubts remain about a residual
autonomic function, providing some emotional
awareness.
3,5
Disclosures The author reports no conflict of interests.
Funding statement Covered by the Institute of Neurology and
Neurosurgery, Havana, Cuba.
Editorial responsibility This submission was handled by
Dr. Stephan K. W. Schwarz, Editor-in-Chief, Canadian Journal of
Anesthesia/Journal canadien d’anesthe
´sie.
References
1. Shemie SD, Wilson LC, Hornby L, et al. A brain-based definition of
death and criteria for its determination after arrest of circulation or
neurologic function in Canada: a 2023 clinical practice guideline.
Can J Anesth 2023; 70: 483–557. https://doi.org/10.1007/s12630-
023-02431-4
2. Greer DM, Shemie SD, Lewis A, et al. Determination of brain
death/death by neurologic criteria: the World Brain Death Project.
JAMA 2020; 324: 1078–97. https://doi.org/10.1001/jama.2020.
11586
3. Machado C. Brain Death: A Reappraisal. New York: Spinger
Science?Business Media, LLC; 2007.
4. Pallis C. Defining death. Br Med J (Clin Res Ed) 1985; 291:
666–7.
5. Machado C. Jahi McMath: a new state of disorder of
consciousness. J Neurosurg Sci 2020; 65: 211–3.
https://doi.org/10.23736/s0390-5616.20.04939-5
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
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